The occurrence of zero effective mass of electrons at the vicinity of the Dirac point is expected to create new paradigms for scientific research and technological applications, but the related discoveries are rather limited. Here, we demonstrate that a simple architecture composed of graphene quantum dots sandwiched by graphene layers can exhibit several intriguing features, including the Dirac point induced ultralow-threshold laser, giant peak-to-valley ratio (PVR) with ultra-narrow spectra of negative differential resistance and quantum oscillations of current as well as light emission intensity...

A novel probabilistic Bayesian strategy is proposed to resolve highly coeluting peaks in high-resolution GC-MS (Orbitrap) data. Opposed to a deterministic approach, we propose to solve the problem probabilistically, using a complete pipeline. First, the retention time(s) for a (probabilistic) number of compounds for each mass channel are estimated. The statistical dependency between m/z channels was implied by including penalties in the model objective function. Second, Bayesian Information Criterion (BIC) is used as Occam's razor for the probabilistic assessment of the number of components...

Comprehensive three-dimensional gas chromatography with time-of-flight mass spectrometry (GC(3)-TOFMS) creates an opportunity to explore a new paradigm in chemometric analysis. Using this newly described instrument and the well understood Parallel Factor Analysis (PARAFAC) model we present one option for utilization of the novel GC(3)-TOFMS data structure. We present a method which builds upon previous work in both GC(3) and targeted analysis using PARAFAC to simplify some of the implementation challenges previously discovered...

La atom reactions with 1-butyne and 2-butyne are carried out in a laser-vaporization molecular beam source. Both reactions yield the same La-hydrocarbon products from the dehydrogenation and carbon-carbon bond cleavage and coupling of the butynes. The dehydrogenated species La(C4H4) is characterized with mass-analyzed threshold ionization (MATI) spectroscopy and quantum chemical computations. The MATI spectra of La(C4H4) produced from the two reactions exhibit two identical transitions, each consisting of a strong origin band and several vibrational intervals...

Photolysis is a core natural process impacting the fate of some sulfonamide antibiotics in sunlit waters. In this study, sunlight-induced phototransformation of sulfathiazole was investigated. A photolytic quantum yield of 0.079 was obtained in buffered water (pH = 8.0). Different natural organic matter isolates inhibited the photolysis of sulfathiazole by light screening effect. A kinetic model was developed to predict the photodegradation rate of sulfathiazole using the light screening correction factor of the water matrix in the wavelength range of 300-350 nm...

In this study, a novel fluorescent detection system for biological sensing of human albumin (HA) was developed on the basis of the pseudo-esterase activity and substrate preference of HA. The designed near-infrared (NIR) fluorescent probe (DDAP) could be effectively hydrolyzed by HA, accompanied with significant changes in both colour and fluorescence spectrum. The sensing mechanism was fully investigated by fluorescence spectroscopy, NMR and mass spectra. DDAP exhibited excellent selectivity and sensitivity toward HA over a variety of human plasma proteins, hydrolases, and abundant biomolecules found in human body...

Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) is a high throughput, easy to use analytical technique. The simple sample preparation of this technique and its tolerance to the presence of contaminants are among its advantages. In contrast, depending on the matrix used, MALDI can ionize and generates ions in the low m/z range that complicate the interpretation of the spectra of low molecular weight compounds. To address this issue, one can envisage the use of tunable ionic matrices that can reduce the low m/z interferents...

RATIONALE: Affinity mass spectrometry (AMS) is an emerging tool in the field of study of protein-carbohydrate complexes. However, experimental obstacles and data analysis is preventing faster integration of AMS methods in the field of glycosciences. Here we show how analysis of direct ESI-MS AMS data can be simplified for screening purposes, even for complex AMS spectra. METHODS: Direct ESI-MS assay was tested in this study, and binding data for the galectin-3C•lactose complex were analyzed using comprehensive and simplified data analysis approach...

Haloterrigena turkmenica was able to synthesize carotenoids when grown in halobacteria medium. These molecules have antioxidant properties and find application in food, cosmetic, and pharmaceutical fields. The carotenoids were extracted with methanol, separated by RP-HPLC, and identified by mass spectrometry and UV/Vis spectra analyses. The C50 carotenoids were the main pigments, and C30, C40, and C51 carotenoids were also detected. Seven geometric isomers were distinguished for bacterioruberin, monoanhydrobacterioruberin, and bisanhydrobacterioruberin...

Cryopreservation of kangaroo sperm has not been successful so far, and yet there is no promising cryopreservation protocol for these cells available. However, conservation of gametes is extremely important, particularly in the context of preserving endangered species. As spermatozoa are comprised of different membrane systems, the composition of these membranes might account for difficulties in cryopreservation. Lipids, as the main components, affect the physical properties of biological membranes and play a major role in sperm maturation...

Peptide mapping with liquid chromatography-tandem mass spectrometry (LC-MS/MS) is an important analytical method for characterization of post-translational and chemical modifications in therapeutic proteins. Despite its importance, there is currently no consensus on the statistical analysis of the resulting data. In this manuscript, we distinguish three statistical goals for therapeutic protein characterization: (1) estimation of site occupancy of modifications in one condition, (2) detection of differential site occupancy between conditions, and (3) estimation of combined site occupancy across multiple modification sites...

The detection and characterization of highly enriched uranium (HEU) presents a large challenge in the non-proliferation field. HEU has a low neutron emission rate and most gamma rays are low energy and easily shielded. To address this challenge, an instrument known as the dual-particle imager (DPI) was used with a portable deuterium-tritium (DT) neutron generator to detect neutrons and gamma rays from induced fission in HEU. We evaluated system response using a 13.7-kg HEU sphere in several configurations with no moderation, high-density polyethylene (HDPE) moderation, and tungsten moderation...

Lipid oxidation is a process ubiquitous in life, but the direct and comprehensive analysis of oxidized lipids has been limited by available analytical methods. We applied high resolution liquid chromatography-mass spectrometry (LC-MS) and tandem mass spectrometry (LC-MS/MS) to quantify oxidized lipids (glycerides, fatty acids, phospholipids, lysophospholipids and galactolipids) and implemented a platform-independent high-throughput amenable analysis pipeline for the high confidence annotation and acyl composition analysis of oxidized lipids...

Development of gemcitabine (GEM) nanocarriers as theranostic agents for pancreatic cancer chemotherapy has received extensive attention in recent years. A novel enzyme-sensitive albumin-based GEM delivery nanoplatform was developed in this research by simple conjugation of GEM to human serum albumin (HSA) via cathepsin B cleavable peptide GFLG and then complexing with near-infrared (NIR) dye IR780, forming a HSA-GEM/IR780 complex. The successful preparation of HSA-GEM/IR780 complex was confirmed by Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF-MS), UV-vis-NIR absorption spectra and fluorescent emission spectra...

Inter-laboratory reproducibility of Matrix Assisted Laser Desorption Time-of-Flight Mass Spectrometry (MALDI-TOF MS) of anaerobic bacteria has not been shown before. Therefore, ten anonymized anaerobic strains were sent to seven participating laboratories, an initiative of the European Network for the Rapid Identification of Anaerobes (ENRIA). On arrival the strains were cultured and identified using MALDI-TOF MS. The spectra derived were compared with two different Biotyper MALDI-TOF MS databases, the db5627 and the db6903...

The HO2 radical is an important atmospheric molecule that can potentially influence the termination of autoxidation processes of volatile organic compounds (VOCs) that lead to the formation of highly oxygenated multifunctional compounds (HOMs). In this work, we demonstrate the direct detection of the HO2 radical using an iodide-based chemical ionization mass spectrometer (iodide-CIMS). Expanding on the previously established correlation between molecule-iodide binding enthalpy and iodide-CIMS instrument sensitivity, the experimental detection of the HO2 radical was preceded by the quantum chemical calculation of the HO2*I(-) cluster (PBE/aug-cc-pVTZ-PP level), which showed a reasonably strong binding enthalpy of 21...